Help Needed on SB220

[Charles Hugg]

I have a very nice, almost new looking, Heathkit SB-220 HF amplifier that needs some attention.
When I turned it on, it made a loud arching noise and flashed and fried R3, the .82 Ohm Shunt Resistor in the Grid Current Metering circuit. I have replaced the Resistor, but am afread to fire it up because I am not sure what caused the problem in the first place. I have a spare set of 3-500Zs so could replace the tubes in case one of them has gone bad. Does anyone have any ideas on what might  be the problem. Could R3 have just gone bad on its own?
Thanks,
Charlie Hugg, K5MBX
Abilene, Texas          

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